Effect of a supplement of water spinach on digestibility by growing Mong Cai pigs fed a basal diet of rice bran

Taysayavong Lotchana and T R Preston^*

Champasack University

Champasack province, Lao PDR

lotchansouks@yahoo.com

^*University of Tropical Agriculture Foundation, UTA - TOSOLY - Finca Ecológica, Morario - Guapota - AA # 48, Socorro, Santander, Santander del Sur, Colombia

Abstract

Three Mong Cai gilts weighing from 67 to 70 kg were allocated at random to three treatments within a 3*3 Latin Square design with period of 10 days (5 days for adaptation and 5 days for collection of data). The treatments were: RB: rice bran only; RBWS15 rice bran supplemented with 15% of water spinach; and RBWS30 rice bran supplemented with 30% of water spinach. Feeding level was 4% of live weight as dry matter (DM). The ratios of rice bran to water spinach were on a DM basis.

Intake of DM and apparent digestibility of DM and crude protein were increased when water spinach replaced up to 15% of the DM of the basal diet of rice bran. Using the “difference” method it was estimated that the coefficients of apparent digestibility of the DM and crude protein of the water spinach were 99 and 150%, implying that the effects of the water spinach on the digestibility of the mixed diet with rice bran were synergistic.

Key words: Acid indigestible ash, foliages, local breeds, synergism

Introduction

The use of green foliage from vegetables (e.g.: water spinach), forage trees (mulberry) and crop plants (cassava and sweet potato) is a recent development that aims to reduce the costs of pig production by making greater use of locally available, protein-rich, feed resources to replace the expensive, usually imported, soybean and fish meals (Preston 2006). The disadvantage of these feeds for pigs is the associated high content of fibrous cell wall constituents that generally results in increased rate of flow of digesta through the gut, and reduced ileal and total tract nutrient digestibility (Ogle 2006), especially the protein fraction (Rodríguez et al 2009; Chhhay Ty et al 2005a).

The lowest cost and most widely available energy feed in Laos, as in most of SE Asia, is rice bran. The fibre content of rice bran in Laos is relatively high as usually it contains variable amounts of the husk fraction. In this case the role of vegetative protein sources is not only to provide protein, but in many cases will result in a lowering of the overall level of the fibrous cell wall fraction, as happens if water spinach, mulberry leaves or taro foliage (leaf + stem) are the supplementary sources of protein (Table 1)

In a companion experiment water spinach was used as the main source of supplementary protein for Mong Cai and Moo Laat pigs fed a basal diet of rice bran (Taysayavong Lotchana and Preston 2010). The present study aimed to investigate the effect of the water spinach supplement on the digestibility of the basal diet of rice bran.
 

Materials and methods

Location

The experiment was carried out at the Integrated Farming Demonstration center of Champasack University, situated about 13 km from Pakse city, Pakse District, Champasack Province; Laos PDR. The temperature in the area averages 27⁰C (range 22 to 32). The experiment was started on 20^th January and ended on 20^th February 2010.
 

Experimental design

The experiment was a 3*3 Latin Square design arrangement of three dietary treatments applied to three Mong Cai gilts (Table 2):

• RB : Rice bran

• RBW15: Rice bran with water spinach 15% of the diet DM

• RBW30: Rice bran with water spinach 30% of the diet DM

The Mong Cai gilts weighed from 67 to 70 kg. They were housed in individual pens during the 30 days trial. Each experiment period consisted of 10 days; 5 days to adapt to the diets followed by another 5 days for collection of feces and feed refusals.

Animals and management

The three Mong Cai gilts (Photo1) were housed in individual pens with concrete floors. Each pen was 2*2 m and provided with feeders, and automatic water drinkers. The pigs were vaccinated against salmonella disease and de-wormed with Ivermectin prior to beginning the study.

Feeds and feeding

The amounts of feed offered daily were based on a predicted DM intake of 4% of live weight (Table 3).

The rice bran (photo 2) and water spinach (photo 3) were bought in the market every day (Photos 2 and 3).

The water spinach was chopped into small pieces (0.5 cm) and then all the diet ingredients were mixed together before feeding the pigs, which was done in two meals per day at 7.00 hours and 16.00 hours.

Data collection

Feed and feces samples were taken over 5 consecutive days. Samples of feces were collected from the floor of the pens 3-4 hours after the first feed in the morning and stored at -18°C. Care was taken to collect the sample from within the deposited feces, avoiding contact directly with the pen floor. The procedure was repeated for 5 days after which the samples were bulked according to individual animals. Feed samples were taken over the same time period.

Chemical analyses

Feed and feces samples were analysed for acid insoluble ash (AIA) method according to the method of Van Keulen and Young (1977), for DM by micro-wave radiation (Undersander et al 1993) and N, CF and ash according to AOAC (1990).

Samples for AIA determination (5g) were ashed for 4-6 hours in a muffle furnace at 450°C. The ash was transferred to a 600 ml beaker and extracted with 100 ml of a solution of HCl (178 ml concentrated HCl and 1 litre of water) and boiled for 5 minutes. The suspension was then filtered and the solid residue transferred to filter paper and ashed again at 450°C for 6h.  Acid insoluble ash (AIA %) was calculated as:

• % AIA = [initial weight of ash-final weight of ash]/initial weight*100

Calculations of apparent digestibility were made as follows:

• Digestibility of DM = 100-[(100*%AIA in feed)/%AIA in feces]

• Digestibility of nutrients = 100- [[(%AIA feed) * % concentration of nutrient in feed]* 100%]/(%AIA Feces)*(% concentration of nutrient in feces)

Statistical analysis

The data were analyzed using the General Linear Models procedure of ANOVA in the Minitab (2000) software (version 13.1). Sources of variation were: diets, animals, periods and error.

Results and discussion

Chemical composition of the diets

The water spinach had 30% less crude fiber than the rice bran and almost twice as much crude protein content (Table 4). As a result, the crude protein level in the diets increased with the level of water spinach (Table 5).

Feed intake

The DM intake of the diet increased linearly with the increase in the level of water spinach (Table 6; Figure 1). DM intake as a function of live weight was closely related with daily intake of crude protein (Figure 2).

Apparent total tract digestibility

The coefficients of apparent digestibility of DM and CP increased as the level of water spinach in the diet was increased (Table 7; Figures 3 and 4).

The effect of the water spinach at the 15% level appeared to be synergistic. The “difference” method of assessing the digestibility of a supplement assumes that the digestibility coefficients of the basal diet and the supplement are additive.

Dig _{WS =} (Dig _RBWS15 – Dig _RB*0.85)/0.15, where 0.15 is the proportion of water spinach in the diet DM and 0.85 is proportion of rice bran).

When this formula was applied to the observed digestibility coefficients of the RB and RBWS15 diets, the results were: 99 and 150% for the apparent digestibility of the DM and crude protein in the water spinach. Clearly, in this case the effects of the two components of the diet were not additive, especially in the case of the crude protein, and that there was a synergistic impact of the water spinach on the nutritive value of the combined rice bran-water spinach diet.

A similar synergism was reported by Chhay Ty el al (2005b) when they replaced 50% of fresh cassava leaves with fresh water spinach in a basal diet of broken rice for growing pigs. Growth rate on the combined forage supplements was greater, and feed conversion better, than the average of the cassava and water spinach diets fed separately. Similarly, combinations of ensiled mulberry leaves and taro foliage (leaf plus stem), as supplements to rice bran, supported higher coefficients of digestibility of DM, CP, NDF and ADF, than would have been predicted from the arithmetic average of the diets with supplements (Chhay Ty et al 2010).

Conclusions

It is concluded that:

• The DM intakes, and the apparent digestibility of DM and crude protein by Mong Cai gilts, were increased when water spinach replaced up to 30% of the DM of the basal diet of rice bran.
• The coefficients of apparent digestibility of the DM and crude protein of the water spinach, estimated by the “difference” method, were 99 and 150%, implying that the effects of the water spinach on the digestibility of the mixed diet with rice bran were synergistic.

Acknowledgements

We would like to thank the Swedish International Development Agency (Sida) for funding this experiment a part of the MSc program through the MEKARN regional project. We also wish to thank the students from the Faculty of Agriculture of Champasack University for their assistance in ‘the care and feeding of the animals.

References

AOAC 1990 Official Methods of Analysis Association of Official Analytical Chemists 15^th Edition (K Helrick editor) Arlington pp 1230

Chhay Ty and Preston T R 2005a Effect of water spinach and fresh cassava leaves on intake, digestibility and N retention in growing pigs, from: http://www.lrrd.org/lrrd17/2/chha17023.htm

Chhay Ty and Preston T R 2005b Effect of water spinach and fresh cassava leaves on growth performance of pigs fed a basal diet of broken rice, from: http://www.lrrd.org/lrrd17/7/chha17076.htm

Chhay Ty, Khieu Borin and Preston T R 2010 Effect of Taro (Colocasia esculenta) leaf + stem silage and mulberry leaf silage on digestibility and N retention of growing pigs fed a basal diet of rice bran;  Livestock Research for Rural Development. Volume 22, Article # 109; Retrieved; from http://www.lrrd.org/lrrd22/6/chha22109.htm

Minitab 2000 User's guide to statistics; Minitab Statistical Software Version 13.31, Minitab Inc, USA.

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Rodríguez Lylian, Peniche Irina, Preston T R and Peters K 2009 Nutritive value for pigs of New Cocoyam (Xanthosoma sagittifolium); digestibility and nitrogen balance with different proportions of fresh leaves and soybean meal in a basal diet of sugar cane juice.  Livestock Research for Rural Development; Volume 21, Article #16 from: http://www.lrrd.org/lrrd21/1/rodr21016.htm

Taysayavong Lotchana and Preston T R 2010 Effect of rice distillers’ by-product on growth performance and digestibility of Moo Laat and Mong Cai pigs fed rice bran and water spinach

Undersander D, Mertens D R, Theix N 1993 Forage analysis procedures. National Forage Testing Association Omaha pp 154

Van Keulen and Young 1977 Evaluation of acid-insoluble ash as natural marker in ruminant digestibility studies Journal of Animal Science 44:262-266.http://jas.fass.org/cgi/reprint/44/2/282.pdf

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